Hydrogen peroxide has been found for the first time in space, and astronomers are excited - not because it indicates that aliens are bottle blondes, but because it gives clues to how water may be formed.

The discovery was made with the Atacama Pathfinder Experiment telescope (APEX), situated on the 5000-metre-high Chajnantor plateau in the Chilean Andes, which observed a region in our galaxy close to the star Rho Ophiuchi, about 400 light-years away.

This area contains very cold, dense clouds of cosmic gas and dust, in which new stars are forming. While the clouds are mostly made of hydrogen, they contain traces of other chemicals.

"We were really excited to discover the signatures of hydrogen peroxide with APEX," says Per Bergman, astronomer at Onsala Space Observatory in Sweden.

"We knew from laboratory experiments which wavelengths to look for, but the amount of hydrogen peroxide in the cloud is just one molecule for every ten billion hydrogen molecules, so the detection required very careful observations."

Hydrogen peroxide - H2O2 - is clearly linked to oxygen and water, which are critical for life. And because much of the water on our planet is thought to have originally formed in space, scientists are keen to understand how it is created.

It's now thought to form in space on the surfaces of cosmic dust grains - very fine particles similar to sand and soot - when hydrogen is added to oxygen molecules. A further reaction of the hydrogen peroxide with more hydrogen is one way to produce water.

"We don't understand yet how some of the most important molecules here on Earth are made in space," says Berengere Parise of the Max-Planck Institute for Radio Astronomy in Germany.

"But our discovery of hydrogen peroxide with APEX seems to be showing us that cosmic dust is the missing ingredient in the process."